1. Technical Field
The present disclosure relates to a roller or a roller unit of an image scanner, a facsimile, or the like, for example, a paper feeder provided with the roller or the roller unit, and an image reader.
2. Description of the Related Art
In recent years image readers with a paper feeder such as an automatic document feeder (ADF) installed thereon are in common use. A separation roller and a retarding roller, on the opposite side from the separation roller, are disposed in the middle of a document transport path of the paper feeder in order to prevent the feeding of multiple document sheets.
The document which is transported to the separation roller is pinched by the separation roller and the retarding roller. At this time, if two documents enter the space between the separation roller and the retarding roller together, the transportation of the document which comes into contact with the retarding roller, which is rotating backward or is stationary, is prevented, and only the topmost document is separated from the other document and is fed out.
In order to reliably separate the documents, it is necessary to render the area (the nipping amount) over which the separation roller and the retarding roller come into contact with the documents sufficiently large to obtain a sufficient friction force for the retarding roller. Therefore, flexibility is demanded of the retarding roller such that the portion of the retarding roller which comes into contact with the separation roller easily warps. Wear resistance is also demanded of the retarding roller in order to suppress running costs.
Japanese Patent Unexamined Publication No. 2005-82376 discloses a retarding roller which is formed of two types of material in order to realize both flexibility and wear resistance. With this retarding roller, the roller is formed of soft urethane to secure flexibility, and the outer circumferential surface of the roller is covered with ethylene propylene diene M-class rubber (EPDM) to secure wear resistance.